The toddlerease sandy's are pretty roomy but they aren't staydry - you could put in a liner but the rest of the diaper would still be wet against his skin.
Are Fuzzibunz fleece lined? I know they have an XXL option.
The Flips disposable inserts are great! We used them on a long road trip and for a while once we got to our destination. They worked great for our 4 yr old night only. I just doubled up at night for him but it never leaked. They are very trim but absorb a lot.